On 4/6/2010 An earthquake measuring 3.7 on the Richter Scale shook the area of the erupting volcano next to the Eyjafjallajokull ice cap in South Iceland.The earthquake is the strongest to hit the area since seismic activity began to build at the volcano at the beginning of March.

Steinunn Jakobsdottir, an Icelandic Meteorological Office geologist told mbl.is that only very few of the regular quakes in the area since the beginning of last month have measured above 3 on the Richter Scale. Jakobsdottir added that it is not yet known if this afternoon’s quake is an important development or if it should be considered as a large but normal earth movement. The quake has not had any immediate effect on the erupting volcano – neither has it had an immediate impact on the nearby dormant Katla volcano.

Benjamin Franklin made what may have been the first connection between volcanoes and global climate while stationed in Paris as the first diplomatic representative of the United States of America. He observed that during the summer of 1783, the climate was abnormally cold, both in Europe and back in the U.S. The ground froze early, the first snow stayed on the ground without melting, the winter was more severe than usual, and there seemed to be “a constant fog over all Europe, and [a] great part of North America.”

What Benjamin Franklin observed was indeed the result of volcanic activity. An enormous eruption of the Laki fissure system (a chain of volcanoes in which the lava erupts through a crack in the ground instead of from a single point) in Iceland caused the disruptions. The Laki eruptions produced about 14 cubic kilometers of basalt (thin, black, fluid lava) during more than eight months of activity. More importantly in terms of global climate, however, the Laki event also produced an ash cloud that may have reached up into the stratosphere. This cloud caused a dense haze across Europe that dimmed the sun, perhaps as far west as Siberia. In addition to ash, the eruptive cloud consisted primarily of vast quantities of sulfur dioxide (SO2), hydrogen chloride (HCl), and hydrogen fluoride gases (HF). The gases combined with water in the atmosphere to produce acid rain, destroying crops and killing livestock. The effects, of course, were most severe in Iceland; ultimately, more than 75 percent of Iceland¿s livestock and 25 percent of its human population died from famine or the toxic impact of the Laki eruption clouds. Consequences were also felt far beyond Iceland. Temperature data from the U.S. indicate that record lows occurred during the winter of 1783-1784. In fact, the temperature decreased about one degree Celsius in the Northern Hemisphere overall. That may not sound like much, but it had enormous effects in terms of food supplies and the survival of people across the Northern Hemisphere. For comparison, the global temperature of the most recent Ice Age was only about five degrees C below the current average.

There are many reasons that large volcanic eruptions have such far-reaching effects on global climate. First, volcanic eruptions produce major quantities of carbon dioxide (CO2), a gas known to contribute to the greenhouse effect. Such greenhouse gases trap heat radiated off of the surface of the earth forming a type of insulation around the planet. The greenhouse effect is essential for our survival because it maintains the temperature of our planet within a habitable range. Nevertheless, there is growing concern that our production of gases such as CO2 from the burning of fossil fuels may be pushing the system a little too far, resulting in excessive warming on a global scale. There is no doubt that volcanic eruptions add CO2 to the atmosphere, but compared to the quantity produced by human activities, their impact is virtually trivial: volcanic eruptions produce about 110 million tons of CO2 each year, whereas human activities contribute almost 10,000 times that quantity.

By far the more substantive climatic effect from volcanoes results from the production of atmospheric haze. Large eruption columns inject ash particles and sulfur-rich gases into the troposphere and stratosphere and these clouds can circle the globe within weeks of the volcanic activity. The small ash particles decrease the amount of sunlight reaching the surface of the earth and lower average global temperatures. The sulfurous gases combine with water in the atmosphere to form acidic aerosols that also absorb incoming solar radiation and scatter it back out into space.

The eruption of Iceland’s Mt. Eyjafjallajökull that is snarling air travel across Europe is too small thus far to cool down the Earth, according to the Union of Concerned Scientists.

Volcanic ash can cause temporary cooling – the 1991 eruption of Mount Pinatubo in the Philippines did just that for a few years – but the Icelandic volcano’s eruption is “too small to significantly affect the climate,” UCS said Friday.

The group appeared to preemptively criticize climate change skeptics, who argue that human activities cannot drive global temperatures, and other opponents of greenhouse gas emissions curbs.

UCS noted that “even if a volcanic eruption were big enough to temporarily cool the planet, heat-trapping carbon dioxide from burning fossil fuels and destroying forests would still pose a significant threat.”

“Unlike volcanic ash that will leave the atmosphere within a few months or years, carbon dioxide remains there for decades and even centuries,” said UCS climate scientist Brenda Ekwurzel in a prepared statement.

“Overloading the atmosphere with carbon dioxide has put us on the path toward a long-term warming trend, so we really can’t pin our hopes on occasional volcanic eruptions to solve the problem,” she said.

The group also used the occasion of the eruption to caution against the idea of intentionally launching large amounts of sulfur dioxide into the atmosphere as a way to cool the planet.

“We’re already conducting a giant experiment with the planet by injecting so much carbon dioxide into the atmosphere,” Ekwurzel said. “It’s not clear that the potential risks of more human tampering with the climate are worth whatever temporary relief this might provide.”

UCS, an advocacy group for environmental causes, released a short primer on the issue of volcanoes and climate. It notes that when sulfur dioxide from eruptions enters the stratosphere, it converts into particles that “act like tiny mirrors” to reflect sunlight back into space, thereby lowering the planet’s temperature.thehill.com

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